I'm gathering info on starting up a 120gal. cichlid tank with Co2 and hoping anyone out there might be able to help me out. I've been running Co2 in one of my planted tanks for a while now and know that these are my current water peramiters with Co2:

pH 7.0
KH 9
GH 12

From what I read this is not great for cichlids, the pH should be up around 8-8.5. Without Co2 my pH is around 8. If I'm correct I need more buffering compacity (higher KH) so the pH will level out higher. I want to use sand in this tank (eg. Blasting sand) not a buffering substrate such as crushed coral because of looks. I will be using a 30gal. sump tank and was wondering if I cound put the crushed coral in here for better buffering. If I do will I be able to use enough material to make a differance or would it be nessesary to use it in the display tank? Any help would be greatly Appreciated!

Having a pH around 8 should be just fine for the cichlids you are looking at getting. You will not need to add CO2 since it won't be planted right? Malawi cichlids will tear up most plants so elaborate rock formations and a mix of sand and gravel should be just fine for them. They'll be quite happy moving the gravel and the sand around so make sure your rock formations are stable enough that they won't fall during "renovations"._________________"Feminae bene moratea historiam raro faciunt"